The present invention relates to the coating of fasteners, and more particularly to an apparatus and process for applying a coating to elements or fasteners, particularly to the threads of an internally threaded element.
In the field of fastener manufacture, a number of machines and processes have been particularly developed for the application of a coating, or patch, to the threads of a fastener element to provide locking engagement with a mated threaded article. Also, various methods and apparatus for applying locking patches of resilient resin to threaded articles have been previously disclosed. These devices generally include a rotatable table, or transport belt arrangement which is disposed for receiving fastening elements. Such devices also typically convey the fastening elements through a plurality of stations to effect application of the coating to the threads of the threaded article or the fastener element.
For example U.S. Pat. No. 4,054,688 and U.S. Pat. No. 4,100,882 disclose devices for forming patches on fasteners whereby resin particles are deposited on one area of the heated threads of an element, and thereafter, the resin particles are deposited on an additional area of the threads to produce two distinct patches at desired locations. In each of the aforementioned patents, internally threaded articles are retained on a rotatable support member in a selected position by means of a slot which receives a portion of the external surface of a hex head nut. After a discrete patch is applied to the internal threads of the fastener, a turning moment is applied to the fastener to move it such that a different external portion of the thread of the hexagonal element is received by the slot, after which a second discrete patch is applied to the threads of the fastener.
Other disclosed devices are found in U.S. Pat. No. 3,858,262 and U.S. Pat. No. 3,894,509. In U.S. Pat. No. 3,858,262, the disclosed method and apparatus is intended to avoid the difficulties of resin deposit on the end surfaces of the threaded element and is effective to deposit resin on selected threads with a minimum of spatter. In that method and apparatus, a nut or other internally threaded member is heated and the internal threads of the heated nut are sprayed with resin particles which are caught and built up on the heated surfaces to form a locking plastic body. The method and apparatus disclosed in U.S. Pat. No. 3,894,509 includes automatic means to move a succession of the internally threaded elements through various stations in which the elements are subjected to treatment at the various stations. A resilient resin locking patch is formed on the threaded surface of the elements by deposition of heat fusible resin powder and thereafter, the elements are unloaded.
U.S. Pat. No. 3,416,492 and U.S. Pat. No. 4,366,190 are further disclosures directed to methods and apparatus wherein a self-locking internally threaded element is manufactured having a locking body of resilient resin provided to the threads. In these patents, however, the resin is provided over 360.degree. of arc of a portion of the internal threads.
As will be observed from a review of the above patents, development of machines and processes for manufacturing threaded articles having a coating or patch applied to the threads has been prevalent. Furthermore, many of the devices disclosed in the prior art have proved to be successful in meeting the specific requirements of the marketplace at the time they were developed. However, with the employment of machines of the type described for not only applying locking patches to a threaded article, but for the application of Teflon (a registered trademark of Dupont Corporation) and a variety of other resin type materials to fasteners, threaded articles and the like for protection, masking, insulating and lubricating of fasteners and the threads of such articles, a specific need has arisen for a machine and process having improved control over the size, shape and extent of the applied coating or patch. Moreover, a machine which is improved in function and operation, improved in efficiency and of simpler construction than those presently found in the marketplace is also desired.
It is therefore an object of the present invention to provide an apparatus and process for the manufacture of internally threaded articles which has improved control of the application of coating material to the fastener or similar article and particularly to the threaded portion of such elements.
A further object of the invention is to provide apparatus having increased reliability and flexibility, as well as reduced set up time over apparatus of the prior art. Furthermore, it is desired to provide a process and apparatus which has improved operational efficiency and flexibility over prior art devices and processes.
Yet another object of the invention is to provide apparatus and process for the manufacture of internally threaded elements wherein the coating operation, including but not limited to the control and definition of the coating, is achieved by a simply constructed cam device.